To learn more about detecting and recording earthquakes, visit the following web sites:

Did You Feel It?, USGS
Contribute your intensity observations of an earthquake that you experienced.

Earthquakes and Seismicity, USGS
Describes the energy released by an earthquake. Includes a good explanation of the difference between intensity and magnitude.

Earthquake Intensity Database Search, NOAA
Includes an earthquake intensity location map of North America. Allows searches for specific earthquakes by city and state, so you can look up the intensity of earthquakes that have shaken your community.

To learn more about the ways earthquakes are measured, visit the following web sites:

How are Earthquakes Studied?, Michigan Technological University
Includes a photograph and description of the first device used to detect earthquakes and an illustration showing how seismograms are generated.